Audio contents such as those in compact discs (CDs) and digital versatile discs (DVDs) and those distributed over networks are typically composed of channel-based audio.
A channel-based audio content is obtained in such a manner that a content creator properly mixes multiple sound sources such as singing voices and sounds of instruments onto two channels or 5.1 channels (hereinafter also referred to as ch). A user reproduces the content using a 2 ch or 5.1 ch speaker system or using headphones.
There are, however, an infinite variety of users' speaker arrangements or the like, and sound localization intended by the content creator may not necessarily be reproduced.
In addition, object-based audio technologies are recently receiving attention. In object-based audio, signals rendered for the reproduction system are reproduced on the basis of the waveform signals of sounds of objects and metadata representing localization information of the objects indicated by positions of the objects relative to a listening point that is a reference, for example. The object-based audio thus has a characteristic in that sound localization is reproduced relatively as intended by the content creator.
For example, in object-based audio, such a technology as vector base amplitude panning (VBAP) is used to generate reproduction signals on channels associated with respective speakers at the reproduction side from the waveform signals of the objects (refer to non-patent document 1, for example).
In the VBAP, a localization position of a target sound image is expressed by a linear sum of vectors extending toward two or three speakers around the localization position. Coefficients by which the respective vectors are multiplied in the linear sum are used as gains of the waveform signals to be output from the respective speakers for gain control, so that the sound image is localized at the target position.